hapter 1 introduction - bs publications · 2015. 5. 22. · 2 geology, tectonics and hydrocarbon...
TRANSCRIPT
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1
CHAPTER - 1
INTRODUCTION
India is having a very special distinction, wherein the setup of various sedimentary basins, very rich in hydrocarbons both on Eastern and Western Offshore India can be compared to a invaluable gold necklace studded with Gems and Precious Stones adored on a Pretty Queen’s neck.
A careful attempt has been made to integrate the valuable data on various Indian offshore basins of both East and West Coasts. To understand the basin evolution of this type, the author feels that the reader should have a basic knowledge on the Plate Tectonics, especially with reference to Indian Plate Movements, with varied divergent passive continental margins and also convergent margins in geological times in the formations of sedimentary basins. Accordingly, a very comprehensive chapter is included on the Plate Tectonics and also a map on Tectonics of India depicting various tectonic elements.
In the process of integrating valuable data in bringing out this volume, an attempt has been made to give an alternative interpretation wherever it is required, for better understanding the tectonics, basin evolution and inturn to focus on the future exploration needs of the country.
One special chapter is included on the demanding alternate source of energy which is drawing the attention of the whole world that is the ‘Gas Hydrates’. Favourably Indian Offshore Basins are very rich in gas hydrates. Incidentally, the estimated amount of natural gas in the gas hydrate accumulations of the world greatly exceeds the volume of all the known conventional gas resources. Gas hydrate reserves are estimated to be more than double the known reserves of fossil fuel, as per C.N.R.Rao, founder and Honorary President of Jawaharlal Nehru Centre of advance research and Kuznetsov, Director of Organic Chemistry, Russia. Rightly, Government of India is focusing and concentrating its efforts on ‘Gas Hydrate – Exploration & Production’ and a road map is drawn to achieve the goal in the very near future.
Since the scope and subject of this book is quite large and open, only a short brief with few details are given on the producing fields and also on oil/gas discoveries.
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2 Geology, Tectonics and Hydrocarbon Prospects Off Shore Sedimentary Basins of India
2
CHAPTER - 2
SEDIMENTARY BASINS OF INDIA
The sedimentary basins of India onland and offshore up to 200 m isobaths have an aerial extent of about 1.79 million Sq. Kms. An additional area of about 1.35 million sq. kms. has been estimated for the deep waters beyond 200 m isobaths. The total area thus works out to be 3.14 million Sq. Kms. All together, 26 major sedimentary basins are grouped into four categories based on the geological history, tectonic evolution, accumulated sediments and on their present status of exploration and prospectivity (Fig. 2.1). The categorization was earlier made by ONGC, essentially to prioritise their exploratory efforts. These sedimentary basins have been in age from Proterozoic to Cenozoic. The classification of the four categories / groups is as under.
Category I Basins
Category I basins are proved petroliferous basins with commercial production: Basins included are Bombay Offshore, Cambay Basin, Cauvery Basin, Krishna‐Godavari Basin, Assam Shelf, Tripura‐Cachar Basin and Rajasthan Basin.
Category II Basins
Category II basins are sedimentary basins with known occurrence of hydrocarbons but not on commercial production.
Such as Kutch, Mahanadi, Andaman & Nicobar, Himalayan Foot Hills and Bengal Basins.
Category III Basins
Category III basins are those, in which significant shows of hydrocarbons have not yet been found, but which on general geological considerations are assumed to be prospective.
Himalayan Foreland, Ganga, Vindhyan, Saurashtra and Kerala‐Konkan fall under this category.
Category IV Basins
Category IV basins are those, which on analogy with similar hydrocarbon producing basins in the world are deemed to be prospective. The hydrocarbon potential of such basins in India is still uncertain and yet to be established.
Karewa, Spiti‐Zanskar, Satpura, Rewa‐ Damodar, Narmada, Deccan Synclise, Bhima‐Kaladgi, Pranhita Godavari, Bastar and Chhattisgarh basins are under this category.
Besides the above four categories, Indian deep water basins located beyond 400 m bathymetry are exclusively categorised.
The geology and prospectivity of these basins are getting unfolded as exploratory efforts, are intensified in these areas in the last decade and half. In the process, some of the basins which are in the lower category have been upgraded to the next category depending on the exploration efforts and success. For e.g. Cauvery, Krishna‐Godavari, Tripura‐Cachar, Rajasthan basins which were originally placed in Category‐III
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Sedimentary Basins of India 3
were upgraded to Category‐I. The detailed break‐up of sedimentary basins as per the categorisation is shown in the Table 2.1.
(Courtesy DGH)
Fig. 2.1
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4 Off hore Sedimentary Basins of India Geology, Tectonics and Hydrocarbon Prospects
Table 2.1: Categorisation of Sedimentary Basins
Category Basin Basinal Area (Sq. Km)
Onland Offshore Total
UPTO 200 M ISOBATH
I Cambay
Assam Shelf
Mumbai Offshore
Krishna Godavari
Cauvery
Assam‐Arakan Fold Belt
Rajasthan
51,000
56,000
‐
28,000
25,000
60,000
126,000
2,500
‐
116,000
24,000
30,000
‐
‐
53,500
56,000
116,000
52,000
55,000
60,000
126,000
SUB TOTAL 346,000 172,500 518,500
II Kutch
Mahanadi‐NEC
Andaman‐Nicobar
35,000
55,000
6,000
13,000
14,000
41,000
48,000
69,000
47,000
SUB TOTAL 96,000 68,000 164,000
III Himalayan Foreland
Ganga
Vindhyan
Saurashtra
Kerala‐Konkan‐Lakshadweep
Bengal
30,000
186,000
162,000
52,000
‐
57,000
‐
‐
‐
28,000
94,000
32,000
30,000
186,000
162,000
80,000
94,000
89,000
SUB TOTAL 487,000 154,000 641,000
IV Karewa
Spiti‐Zanskar
Satpura‐South Rewa‐Damodar
Narmada
Deccan Syneclise
Bhima‐Kaladgi
Cuddapah
Pranhita‐Godavari
Bastar
Chhattisgarh
3,700
22,000
46,000
17,000
273,000
8,500
39,000
15,000
5,000
32,000
‐
‐
‐
‐
‐
‐
‐
‐
‐
‐
3,700
22,000
46,000
17,000
273,000
8,500
39,000
15,000
5,000
32,000
SUB TOTAL 461,000 ‐ 461,200
TOTAL 1,390,200 394,500 1,784,700
Deep
waters
Kori‐Comorin
85°E
Narcodam
‐
‐ 1,350,000
GRAND TOTAL ‐ ‐ 3,134,700
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Sedimentary Basins of India 5
The total hydrocarbon resources inclusive of deep waters are estimated at 28 billion tons of oil and oil equivalent of gas. As on April 2008, an initial inplace of 9.13 billion tons, of which recoverable reserves of 3.4 billion tons have been established indicating an upgradation of 32% of resources to reserve category. With more and more exploration efforts further upgradation can be achieved. However, the resources as estimated by DGH stands at 32 billion tons (O + OEG) – Table 2.2.
Table 2.2: Basin‐wise Hydrocarbon Resources
(MMT)
Basin Offshore Onland Total
Mumbai 9,190 ‐ 9,910
Assam‐Arakan Fold Belt ‐ 3,180 3,180
Cambay ‐ 2,050 2,050
Upper Assam ‐ 1,860 1,860
Krishna‐Godavari 555 575 1,130
Cauvery 270 430 700
Rajasthan ‐ 380 380
Kutch 550 210 760
Andaman‐Nicobar 180 ‐ 180
Kerala‐Konkan 660 ‐ 660
Saurashtra Offshore 280 ‐ 280
Ganga Valley ‐ 230 230
Bengal 30 160 190
Himalayan Foreland ‐ 150 150
Mahanadi 100 45 145
Deepwater * 7000 ‐ 7,000
GRAND TOTAL 18,815 9,270 28,085
(After DGH)
*Hydrocarbon resources in Deepwater off East Coast are likely to increase further by about 400 MMT as per interpretation results of
reconnaissance surveys carried out by DGH.
These resource potentials do not include the gas hydrate resources. The total prognosticated gas resources from the gas hydrates in the country is placed additionally at 1894 TCM.
Indian Stratigraphy
The stratigraphy of Indian basins in general as established by different authors is indicated in Table 2.3 & 2.4.
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6 O
ff Sh
ore
Sedi
men
tary
Bas
ins
of In
dia
Geo
logy
, Tec
toni
cs a
nd H
ydro
carb
on P
rosp
ects
Table 2.3: Gen
eral Geo
logical Succession in differen
t parts of Ind
ia and
BURM
A Prof. M.S. Krishnan, 1943
Stan
dard
Scale
Northern
Him
alaya
Baluchistan
Arc
Salt Ran
ge
& Potwar
Kashmir‐
Hazara
Simla‐
Garhw
al
Assam
Bu
rma
Peninsula
Coastal
Areas
Recent …..
Alluvium
Sand
s, Loe
ss
Alluvium
, Loess
Alluvium
& C
Alluvium
& C
Alluvium
, River gravels
Alluvium
, River gravels
Alluvium
Kh
adar
Alluvium
sand
s
Pleistocen
e Older
Alluvium
, gravels,
moraine
s
Older
alluvium
, sand
s
Older
alluvium
, sand
s
Older alluvium
, moraine
s Upp
er Karew
a
Older
alluvium
, moraine
s
Older
alluvium
, gravels
Older
alluvium
, River
terraces
Older alluvium
, Bh
angar, Cave
depo
sits, river
terraces
Raised
be
ache
s,
Porbande
r ston
e etc.
Pliocene
Upp
er
Miocene
……
Siwalik Sy.
Manchhar Sy.
Siwalik Sy.
Lower Karew
a Siwalik Sy.
Siwalik Sy.
Dihing S.
Irrawaddy
Sy.
…….
Siwalik Sy.
Karaikal B.
Quilon B.
Cudd
alore
Sst. Etc.
Middle
Miocene
Lower
Miocene
…..
Mekran Sy.
Flysch, B
ugti
B. Gaj S.
Murree S.
Murree S.
Fatehjang zone
Kasauli B.
Dagshai B.
Tipam S.
Surm
a S.
Upp
er Pegu
S.
…….
Gaj s.
Oligocen
e ……
Nari S.,
Khojak Shales
…....
…….
……..
Barali S. (in
part).
Lower Pegu
S.
……..
Nari S.
Dwaraka B.
Eocene
……
Eocene
……
Kirthar S. Laki
S. Ranikot S.
Chharat S
. Kirthar S.
Laki S.
Ranikot S
.
Chharat S
. Hill
Lst.
Ranikot S
.
Subathu
B.
Barail S.
Jaintia
S.
Sylhet Lst
Disang S.
Cherra Sst.
Yaw and
Po
ndaung
Stages.
Tabyin, Tilin,
and
Laun
gshe
stages
…..
Deccan Trap
and
Intertrapp
eans,
Lametas
Kirthar S.
Laki S.
Ranikot S
.
Upp
er
Cretaceo
us
Upp
er
Cretaceo
us
Chikkim S.
Cardita
Be
aumon
ti B.,
Pab Sst.
Upp
er
Cretaceo
us
Upp
er
Cretaceo
us
……
Disang S. (in
part) U
pper
Cretaceo
us
Axial S. (in
part)
Negrais S.
Deccan Trap
and
Intertrapp
eans,
Lametas
Bagh
B.
Trichino
poly
Cretaceo
us
Lower
Cretaceo
us
Giumal Sst.
Parh Lst.
Lower
Cretaceo
us
Giumal S.
Orbito
lina Lst.
…..
….
Lower
Cretaceo
us
Umia B. ….
Umia B.
6
Table 2.3: Con
td…
-
Se
dim
enta
ry B
asin
s of
Indi
a
Stan
dard
Scale
Northern
Him
alaya
Baluchistan
Arc
Salt Ran
ge
& Potwar
Kashmir‐
Hazara
Simla‐
Garhw
al
Assam
Bu
rma
Peninsula
Coastal
Areas
Jurassic …
.. Spiti Shales
Koto Lst.
Massive Lst.
Crinoidal Lst.
Jurassic
Spiti shale
Jurassic
? Tal. S.
…..
Nam
yau B.
? Loi‐a
n B.
Jubb
ulpo
re
Kota Rajmahal
Katrol Chari
Patcham
Triassic …
.. Triassic …..
U. Triassic
Triassic
Triassic
? Shali Lst.
? Krol S.
…..
Napen
g B.
Maleri
Pachmarhi
Panche
t
……
Perm
ian …
Prod
uctus B.
Syringothyris
Lst.
Perm
o‐Carbon
iferous
Prod
uctus
Lst.
Speckled
Sst.
Agglomertic
Slates,
Zewan
B.
? Infra‐
Krol.
…..
Upp
er
Plateau Lst.
Mou
lmein
Lst.
Raniganj S.
Barren
Measures,
Barakar S
.
……
Up.
Carbon
iferous ……
……
Conu
laria
and
Euryde
sma
B. Bou
lder
Bed
Agglomeratic
sh.
Gangamop
teris
B. Tanakki
Boulde
r B.
……
?Blaini
boulde
r Be
d.
……
Subansiri B.
?Umaria B.
Talchir bo
ulde
r B.
……
Middle & L.
Carbon
iferous Po
Series
Fene
stella Sh.
……
……
Fene
stella sh.
……
……
L. Plateau
Lst.
……
……
Devon
ian
Muth Qtzt.
……
…….
Muth Qtzt
Devon
ian
(Chitral)
? Jaun
sar
S.
……
Padaukpin
Lst. W
etwin
Sh.
……
……
Silurian
…
Silurian
….
……
…….
Silurian
……
……
Zebingy S.
Nam
shim
S.
……
……
Ordovician
Ordovician
……
…….
Ordovician
……
……
Naungkangyi
S. M
awson
S.
……
……
Cambrian ….
Cambrian …
. ……
Cambrian
Cambrian
? Deo
ban
Lst.
……
Bawdw
in
volcanic
?Mergui S.
Vind
hyan
Sy.
……
Algon
kian
Haimanta Sy.
……
Attock
Slates
Dogra Slates
Simla
Slates
Buxa S.
Daling S.
Darjeeling S.
Chaung.
Magyi S.
Cudd
apah
Sy.
Delhi Sy.
……
Archa
ean
Vaikrita Sy.
……
?Salkhala S.
Gne
isses
Chail S.
Jotogh
S.
Shillon
g s.
Gne
isses
Mogok
S.
Gne
isses
Dharw
ar Sy.
Aravalli Sy. Etc.
Gne
isses
……
7
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Off hore Sedimentary Basins of India Geology, Tectonics and Hydrocarbon Prospects 8
International statigraphic nomenclature, as established by International Commission on Statigraphy is shown in Table 2.5.
Table 2.5: International Statigraphic Chart
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